The purpose of this project is to determine the efficacy of choline chloride (12gm/day) and levodopa (2gm/day) in the treatment of senile dementia. The project involves two separate clinical trials (60 patients in each), using a double-blind, crossover design to compare six-week treatment periods with the active compound and placebo. About two-thirds of the study sample (80 patients) will have entered the study by the end of the second study year. An interim data analysis for drug efficacy, as well as an evaluation of the diagnostic and cognitive evaluation measures are currently being carried out. The proposed completion of this project in the third study year will provide vital information concerning treatment efficacy as well as fostering major advances in cognitive evaluation and differential diagnosis.